• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.93-96
• /
• 2000

This study discusses a non-contact optical technique, phase shifting electronic speckle pattern interferometry, that is well suited for a deformation measurement. However, the phase shifting method has difficulties for determinating a deformation quantitatively beacuse of the characteristics of arctan function. In order to solve this problem, phase unwrapping methods has been studied during the last few years. In this study, using phase unwrapping based on line by line scanning phase shifted fringe patterns are studied to determinate a deformation quantitatively. Also least square fitting method is applied to reduce noise and improve image resolution.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.04b
• /
• pp.308-313
• /
• 1995

Non-destructive inspection techniques using laser have been broading their application areas as well as growing their measurement skills together with the rapid development of circumferential technology like fiber optics and computer. The remarkable inspection technique using laser speckle, so-called ESPI is aleady on the stage of on-line testing with commercial products in other nations. Especially, this technique is expected to be applied to the nuclear industry. Because it is proper for the vibration measurement and it can be applied to objects of a high temperature. This paper describes the use of the ESPI system for measuring vibration patterns on the reflecting objects. Using this system, high-quality Jo fringers fso that fringe shift algorthms can be used to determine vibration interferograms recorded by the ESPI system.

• Journal of Applied Reliability
• /
• v.5 no.4
• /
• pp.439-450
• /
• 2005

Thermal deformation of Digital Television effect friction noise directly. However there was no methods to find and to solve the thermal friction noise which is huge problem in Digital Television In this study, to figure out occurrence cause of friction noise of the product, we measured thermal deformation of the product to organize a triggering device united with Laser Doppler Vibrometer(LDV) which turned occurrence moment of thermal friction noise into a possibility to measure. In conclusion, we could offer an effective information of design, and ensured ESPI(Electronic Speckle Pattern Interferometry) measure technique which is more detailed than the past way.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.34 no.1
• /
• pp.18-22
• /
• 2014

Residual stresses that occur during the welding process, are the main cause of failure and defects in welded structures. This paper, presents the use of an electronic processing laser speckle interferometer to measure the residual stress of a welded pipe for a nuclear power plant. A tensile testing machine was used to evaluate a welded pipe that failed in compression. The inform plane deformation and modulus of elasticity of the base metal and welds were measured using an interferometer. Varying the load on the welded pipe had a larger effect on the deformation of the base metal the other properties of the base metal and welds. The elastic moduli of the base metal and weld of the welded pipe were 202.46 and 212.14 GPa, respectively, the residual stress was measured to be 6.29 MPa.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.2
• /
• pp.81-86
• /
• 2005

This paper proposes a non-destructive ESPI technique to quantitatively evaluate defects inside a semiconductor package. The inspection system consists of the ESPI system, a thermal loading system and an adiabatic chamber. The technique is high feasibility for non-destructive testing of a semiconductor and overcomes the weaknesses of previous techniques, such as time-consumption and difficult quantitative evaluation. Most defects are classified as delamination defects, resulting from the insufficient adhesive strength between layers and from non-homogeneous heat spread. Ninety percent of the tested samples had delamination defects which originated at the corner of the chip and nay be related to heat spread design.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.5
• /
• pp.90-97
• /
• 2001

An electronic speckle pattern interferometry (ESPI) system for measuring tensile properties under micro-tensile testing has been developed. The system consists of an optical system and an image processing system. In the optical system, optical components for measurement of in-plane deformation are arranged on the path of He-Ne laser. In the image processing system, the window-based program for acquiring speckle pattern interferometric image was developed and deformation in a small specimen is continuously evaluated during the test. Using this system, tensile strain of copper foil was measured during tensile testing. Tensile specimen had the thickness and width of 22 and 500 ${\mu}{\textrm}{m}$, respectively. Tensile properties, including the elastic modulus, yielding strength and tensile strength, of the copper were evaluated and also plastic exponent and coefficient in the Ramberg-Osgood relationship were evaluated from the stress-strain curve.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.7
• /
• pp.597-601
• /
• 2008

Currently knowledge of strain in welds has mainly been obtained from strain gaging method: that is directly attaching most of the material to the gage. The very few non-contact methods are still in the early stage. One of the non-contact methods is by the use of the laser that has high-level of the accuracy for the measurement, and this laser also has excellent characteristics on which many studies for its applications are focused throughout the many fields. A method of study is on the measurement of the strain caused by the characteristics of the spot welded zone which is used with 3-D ESPI system that is functionally modified through the laser ESPI(Electronic Speckle Pattern Interferometry) system. This system employed the SGCC 1.2t which are mainly used for the steel plate such as automobile, structure, building material and electronic appliances.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.1
• /
• pp.1-7
• /
• 2014

A stretchable polymeric membrane shaped diffuser was used to homogenize the coherent laser beam. The developed RGB module was used to focus and defocus test by beam combiners. Average oscillation frequency was set at 180Hz~300Hz and it resulted in the best homogenization effect in visual range. The blue laser module turned out to be the worst case for the transmission and primary reason is believed to be the short length of irradiated laser beam. The developed system removed the speckling and the brightness was decreased by 10 ~ 20% for the RGB laser. Overall the brightness was decreased by 13% and homogenity with respect to the temporal axis was improved from 30fs to 110fs.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.28 no.3
• /
• pp.302-308
• /
• 2008

Composite materials are widely used as structural materials for aerospace engineering because of its excellent mechanical properties such as light weight, high stiffness, and low thermal expansion. In driving, impact damage is one of the common but dangerous damages, caused by internal failure of the laminas interface which is not detected by in the surface. Many techniques to detect defects or delaminate between laminates have been reported. Shearography is a kind of laser speckle pattern interferometry with the advantages of non-destructive, non-contact, high resolution and displacement slope measurement. In this paper, the shearography is used to evaluate non-destructively impact damaged surface of the composite material and a measuring method using shearography for the thermal deformation of a impact damaged composite material is discussed. The basic principles of the technique are also described briefly.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.8 no.4
• /
• pp.79-86
• /
• 1999

Electronic Speckle Pattern Interferometry(ESPI) is a powerful tool to measure the vibration mode shape and resonance frequency for modal analysis. As for ESPI this method is very suited for full-field measurement of objects in industrial areas because the interferograms are recorded with a video camera and evaluated in real-time with a computer. In this study We performed experiments at the same constraint conditions as disk brake of the practical vehicle as far as possible and obtained the resonance frequencies and vibration mode shapes by using time-averaged ESPI at once. Finally to assure the expetimental results by time-averaged ESPI we also compare those with results obtained by Laser Doppler Vibrometer and obtained good agreement.